Mautodontha (Garrettoconcha) spelunca, Sartori, André F., Gargominy, Olivier & Fontaine, Benoît, 2014

Sartori, André F., Gargominy, Olivier & Fontaine, Benoît, 2014, Radiation and decline of endodontid land snails in Makatea, French Polynesia, Zootaxa 3772 (1), pp. 1-68 : 26-27

Mautodontha (Garrettoconcha) spelunca sp. nov.

Figures 3A–C ; 14C; 17; 35I; 37C; 39.

Examined material (207 specimens). Holotype: MNHN 25582, Mk13. Paratypes: MNHN 25583, 8 shells, Mk13. Additional material: 198 shells, Mk13.

Type locality. West coast, approximately 3 km south of Temao, Makatea (15.85189°S; 148.28018°W). Cave. Limestone, alt. 10 m; station Mk13.

Diagnosis. Shell less than 5 mm in diameter, depressed, without flammulations; teleoconch sculptured by narrow, tall, relatively crowded primary axial ribs (> 90 ribs on body whorl); umbilicus V-shaped; palatal wall with 3 or occasionally 2 low barriers; parietal wall with 2 conspicuous barriers, occasionally accompanied by 1 trace.

Description. Shell depressed, white, without flammulations. Shell wall thin, pellucid; periostracum adherent, shiny. Apex and spire elevated; later whorls descending more rapidly. Apical and umbilical sutures impressed; whorls rounded to very slightly flattened above periphery; basal wall uniformly rounded, columellar wall broadly rounded, their junction usually marked by a tighter curvature. Transition between protoconch and teleoconch indistinct. Axial sculpture of the protoconch initially composed of pairs of fine riblets separated by interspaces 8– 12 times the width of an individual riblet; riblets within each pair initially separated by a narrow interspace c. 1–2 times their width, subsequently coming closer and progressively merging into prominent ribs, which comprise the primary sculpture of the teleoconch. Single axial riblets between pairs occurring approximately from the second quarter of the first whorl onwards, progressively increasing in number and transitioning into the secondary sculpture of the teleoconch. Spiral sculpture of the protoconch composed of approximately equidistant lirae with interspaces 3–4 times their width, fading out approximately on the first quarter of the second whorl. Teleoconch sculptured by tall, narrow axial ribs, with interspaces 3–4 times their width, overlaid by a secondary ornament of riblets, with interspaces c. 3–6 times their width. Teleoconch devoid of spiral sculpture. Umbilicus deep, V-shaped. Peristome crescent-shaped; columellar lip slightly reflected. Palatal wall usually with 3 low barriers, all extending c. 1/16 whorl, descending abruptly anteriorly and posteriorly, recessed within the aperture; barrier 1 at the junction of basal and columellar walls, commonly trace-like, occasionally lacking, slightly more deeply recessed than the others; barriers 2 and 3 basal in position, similar in prominence, with an interspace slightly smaller than that between barriers 1 and 2. Parietal wall with 2 prominent barriers, both extending c. 1/8 whorl, descending abruptly anteriorly and posteriorly, not recessed within the aperture, similar in prominence. One parietal trace occasionally present between the barriers. Other shell features that can be expressed numerically are shown in Table 2 .

Remarks. M. (G.) spelunca is similar to M. (G.) makateaensis in the presence of three palatal and two parietal barriers, but differs from that species in its larger shell size, more closely-set sculpture and usually wider umbilicus.

M. (G.) spelunca is also larger and usually has a wider umbilicus than M. (G.) passosi , from which it is also distinguished by bearing three rather than four palatal barriers.

Etymology. From spelunca (Latin) , meaning cave. This species is only known from a cave on the west side of Makatea.

Figures

FIGURE 3. A – C. Photographs of Mautodontha (Garrettoconcha) spelunca sp. nov. (MNHN 25583, paratype 3), showing the placement of measurements used in this study; D. Peristome of Mautodontha (Mautodontha) daedalea (MNHN 25587, specimen 9), showing the numbering scheme for apertural barriers used in this study. Abbreviations: ah, aperture height; aw, aperture width; d, shell diameter; h, shell height; nr, number of ribs on body whorl (counted from this line to the aperture); nw, number of whorls (line marks the boundary between whorls); sp, spire protrusion; t 1, t 2, barrier traces; u, umbilicus diameter. Scale bars: A – C = 2 mm; D = 0.5 mm.